Day: 20150928

Summary:Women react differently to negative images compared to men, which may be explained by subtle differences in brain function. This neurobiological explanation for women’s apparent greater sensitivity has been demonstrated by researchers in a new study.

“Not everyone’s equal when it comes to mental illness,” said Adrianna Mendrek, a researcher at the Institut universitaire en santé mentale de Montréal and lead author of the study. “Greater emotional reactivity in women may explain many things, such as their being twice as likely to suffer from depression and anxiety disorders compared to men,” Mendrek added, who is also an associate professor at the University of Montreal’s Department of Psychiatry.

In their research, Mendrek and her colleagues observed that certain areas of the brains of women and men, especially those of the limbic system, react differently when exposed to negative images. They therefore investigated whether women’s brains work differently than men’s and whether this difference is modulated by psychological (male or female traits) or endocrinological (hormonal variations) factors.

For the study, 46 healthy participants — including 25 women — viewed images and said whether these evoked positive, negative, or neutral emotions. At the same time, their brain activity was measured by brain imaging. Blood samples were taken beforehand to determine hormonal levels (e.g., estrogen, testosterone) in each participant.

The researchers found that subjective ratings of negative images were higher in women compared to men. Higher testosterone levels were linked to lower sensitivity, while higher feminine traits (regardless of sex of tested participants) were linked to higher sensitivity. Furthermore, while, the dorsomedial prefrontal cortex (dmPFC) and amygdala of the right hemisphere were activated in both men and women at the time of viewing, the connection between the amygdala and dmPFC was stronger in men than in women, and the more these two areas interacted, the less sensitivity to the images was reported. “This last point is the most significant observation and the most original of our study,” said Stéphane Potvin, a researcher at the Institut universitaire en santé mentale and co-author of the study.

The amygdala is a region of the brain known to act as a threat detector and activates when an individual is exposed to images of fear or sadness, while the dmPFC is involved in cognitive processes (e.g., perception, emotions, reasoning) associated with social interactions. “A stronger connection between these areas in men suggests they have a more analytical than emotional approach when dealing with negative emotions,” added Potvin, who is also an associate professor at the University of Montreal’s Department of Psychiatry. “It is possible that women tend to focus more on the feelings generated by these stimuli, while men remain somewhat ‘passive’ toward negative emotions, trying to analyse the stimuli and their impact.”

This connection between the limbic system and the prefrontal cortex appeared to be modulated by testosterone — the male hormone — which tends to reinforce this connection, as well as by an individual’s gender (as measured be the level of femininity and masculinity). “So there are both biological and cultural factors that modulate our sensitivity to negative situations in terms of emotions,” Mendrek explained. “We will now look at how the brains of men and women react depending on the type of negative emotion (e.g., fear, sadness, anger) and the role of the menstrual cycle in this reaction.”

Summary:Like scratchy-sounding old radio dials that interfere with reception, circuits in the brain that grow noisier over time may be responsible for ways in which we slow mentally as we grow old, according to the results of new studies from UC San Francisco on young and older adults.

The new intracranial and electroencephalogram (EEG) research, published online September 22, 2015, in The Journal of Neuroscience, supports the neural noise hypothesis, which proposes that the signal-to-noise ratio in nerve circuits diminishes with aging and leads to worse performance. The studies were designed and conducted by Brad Voytek, PhD, when he was a postdoctoral research fellow working in the lab of Adam Gazzaley, MD, PhD, professor of neurology, physiology and psychiatry at the UCSF Center for Integrative Neuroscience.

In two new experiments, Voytek, now an assistant professor of cognitive science and neuroscience at UC San Diego, found that background noise in key cortical regions of the brain responsible for higher functions was associated with poorer memorization of visual information, and that this noise also was associated with age. He concluded that neural noise might be the mechanism behind aging-associated loss of cognitive ability, slowing of behavioral responses, uncertain memories and wavering concentration.

“Our measurement of noise seems to show up in aging, just as we thought it would,” Voytek said.

The noise measured in the studies was random signaling that did not fit the pattern of the brain’s natural oscillations. These oscillations are rhythmic patterns of electrical activity generated by nerve cells, or neurons, linked within the brain’s circuitry. This activity occurs in addition to electrical signals generated by individual neurons.

In recent years brain oscillations have become an intense focus of research by Voytek and others seeking to discover any functional roles they might play. Emerging evidence suggests that oscillations might prime nerve circuits to respond more efficiently to stimuli.

“Imagine that individual neurons are like surfers,” Voytek said. “Nearby surfers experience the same waves, which are like the oscillations linking neurons in the brain. But like noise, additional interfering factors often disrupt the perfect wave at different times and different spots along the beach.”

In one experiment on 15 consenting subjects, Voytek collected and analyzed voltage measurements from electrodes placed directly in contact with cortical regions of the brain during surgery by neurosurgeons searching for the specific location that triggered each patient’s seizures. The intracranial study design eliminated detection of confounding signals from muscle. The alert study subjects performed a listening task, which in one of Voytek’s earlier human studies resulted in a high degree of coordinated brain oscillations in these regions. In the new experiment Voytek’s research team found that noise in the frontal cortex and in the temporal cortex was associated with age.

In the second experiment, the researchers collected data from EEG electrodes placed on the scalps of 11 healthy participants between the ages of 20 and 30 and 13 healthy participants between the ages of 60 and 70, while the research subjects performed a visual memorization test.

Researchers flashed one, two or three colored squares for less than one-fifth of a second, gave the subjects almost one second to memorize the colors, and then flashed a second display and asked the participants if the colors matched. The researchers used mathematical algorithms to extract measures of noise in the oscillations from data collected during the interval when the subjects were trying to memorize the colors.

On average, older subjects performed worse than younger subjects. The scientists determined that this poorer performance was due to additional noise in nerve circuits in the visual cortex; neurons did not appear to coordinate as well in generating lower-frequency oscillations. When the researchers accounted for the noise, age was no longer an independent, significant factor in performance in this experiment.

Voytek suggested an analogy. “A big group of friends can have a fairly normal conversation at home,” he said, “but in a crowded bar everyone keeps asking each other, ‘What did you say?’ Similarly, instead of having a normal conversation, the neurons that make up the memory networks in older adults seemed to be talking over one another, leading to a communication breakdown and degrading their memory performance.

“I think these types of experiments will allow neuroscientists to explore the neural underpinnings of cognitive changes across normal aging and in a variety of disease states, including autism, Parkinson’s and schizophrenia, each of which is associated with breakdowns in neural oscillations.”

Children with a good understanding of others’ thoughts are more selective about whom they learn from, new research shows

Date:

September 22, 2015

Source:

Concordia University

Summary:

Children are not as gullible as we might think — and that’s especially true for those who have a good understanding of what’s going on inside someone else’s head, new research confirms.

New research shows that children are not as gullible as we might think — and that’s especially true for those who have a good understanding of what’s going on inside someone else’s head.

In a paper recently published in the British Journal of Developmental Psychology, researchers from Concordia University and the University of Ottawa show that even young children can be selective in whom they prefer to learn from.

“We already know that some preschoolers are more likely to learn from individuals with a history of making accurate claims over individuals who have been inaccurate or ignorant,” says the study’s senior author Diane Poulin-Dubois, a professor with Concordia’s Department of Psychology and researcher with the Centre for Research in Human Development.

“Kids have also been shown to prefer learning from nicer, more confident or more attractive individuals — attributes that don’t have anything to do with intelligence. We speculated that certain social-cognitive abilities might explain some of these learning differences,” she says.

To test the hypothesis, Poulin-Dubois worked with study co-author Danielle Penney and the study’s first author, Patricia Brosseau-Liard, who completed the study while she held a post-doctoral research position at Concordia. Brosseau-Liard is now on faculty at the University of Ottawa’s School of Psychology.

The three researchers took 65 children through a series of tasks that tested their ability to learn new words, as well as their “theory of mind” (ToM) — that is, the intuitive understanding of one’s own and other people’s minds or mental states.

The researchers tested whether the preschool-aged participants were more likely to learn new words from an accurate or inaccurate individual. They also examined whether the children were more likely to learn from a physically strong individual over a weak one. In addition, the researchers embarked on a series of quick ToM tests that required the children to empathize with another individual.

For the ToM tests, the participants were first introduced to several different figurines and given some background information about each: Mr. Jones likes carrots, Linda thinks her cat is hiding in the bushes, Polly and Peter have never seen what’s inside the box.

The children were then asked to theorize about what kind of snack Mr. Jones would want, where Linda would search for her dog and what Polly and Peter would think was inside the box.

A clear pattern emerged: the children who could accurately intuit the figurines’ thoughts and desires were more likely to believe the individuals with the greatest verbal accuracy, rather than those who had demonstrated the greatest strength. That is, the kids with better ToM skills were less gullible.

Brosseau-Liard cautions that theory of mind accounts for only a small variance.

“Even though theory of mind does predict children’s tendency to selectively learn from more accurate individuals, it does not completely explain this ability. There are likely many other variables influencing selective learning, including important social and cognitive attributes,” she says.

Summary:A new study links anxiety, a brain structure called the orbitofrontal cortex (OFC), and optimism, finding that healthy adults who have larger OFCs tend to be more optimistic and less anxious.

The new analysis, reported in the journal Social, Cognitive and Affective Neuroscience, offers the first evidence that optimism plays a mediating role in the relationship between the size of the OFC and anxiety.

Anxiety disorders afflict roughly 44 million people in the U.S. These disorders disrupt lives and cost an estimated $42 billion to $47 billion annually, scientists report.

The orbitofrontal cortex, a brain region located just behind the eyes, is known to play a role in anxiety. The OFC integrates intellectual and emotional information and is essential to behavioral regulation. Previous studies have found links between the size of a person’s OFC and his or her susceptibility to anxiety. For example, in a well-known study of young adults whose brains were imaged before and after the colossal 2011 earthquake and tsunami in Japan, researchers discovered that the OFC actually shrank in some study subjects within four months of the disaster. Those with more OFC shrinkage were likely to also be diagnosed with post-traumatic stress disorder, the researchers found.

Other studies have shown that more optimistic people tend to be less anxious, and that optimistic thoughts increase OFC activity.

The team on the new study hypothesized that a larger OFC might act as a buffer against anxiety in part by boosting optimism.

Most studies of anxiety focus on those who have been diagnosed with anxiety disorders, said University of Illinois researcher Sanda Dolcos, who led the research with graduate student Yifan Hu and psychology professor Florin Dolcos. “We wanted to go in the opposite direction,” she said. “If there can be shrinkage of the orbitofrontal cortex and that shrinkage is associated with anxiety disorders, what does it mean in healthy populations that have larger OFCs? Could that have a protective role?”

The researchers also wanted to know whether optimism was part of the mechanism linking larger OFC brain volumes to lesser anxiety.

The team collected MRIs of 61 healthy young adults and analyzed the structure of a number of regions in their brains, including the OFC. The researchers calculated the volume of gray matter in each brain region relative to the overall volume of the brain. The study subjects also completed tests that assessed their optimism and anxiety, depression symptoms, and positive (enthusiastic, interested) and negative (irritable, upset) affect.

A statistical analysis and modeling revealed that a thicker orbitofrontal cortex on the left side of the brain corresponded to higher optimism and less anxiety. The model also suggested that optimism played a mediating role in reducing anxiety in those with larger OFCs. Further analyses ruled out the role of other positive traits in reducing anxiety, and no other brain structures appeared to be involved in reducing anxiety by boosting optimism.

“You can say, ‘OK, there is a relationship between the orbitofrontal cortex and anxiety. What do I do to reduce anxiety?'” Sanda Dolcos said. “And our model is saying, this is working partially through optimism. So optimism is one of the factors that can be targeted.”

“Optimism has been investigated in social psychology for years. But somehow only recently did we start to look at functional and structural associations of this trait in the brain,” Hu said. “We wanted to know: If we are consistently optimistic about life, would that leave a mark in the brain?”

Florin Dolcos said future studies should test whether optimism can be increased and anxiety reduced by training people in tasks that engage the orbitofrontal cortex, or by finding ways to boost optimism directly.

“If you can train people’s responses, the theory is that over longer periods, their ability to control their responses on a moment-by-moment basis will eventually be embedded in their brain structure,” he said.

Summary:Using a species of butterfly as an example, researchers have demonstrated how insects adapt their offspring to changing environmental conditions. The paper shows that females pass on their own experience to their brood, even if this experience was not necessarily ideal. This rapid adaptation has huge implications for our understanding of speciation in insects.

In their study, the researchers working under Prof. Andreas Erhardt firstly confirmed their earlier results, which showed that parent generations of butterflies can condition their offspring to the quality of forage plants that they experienced as larvae. Secondly, they were able to provide evidence for the first time that the mothers of these offspring change their egg-laying behavior and prefer to deposit their eggs on plants on which they themselves once developed.

The Basel-based environmental scientists showed that young females of the small cabbage white (Pieris rapae) were more precise than their parents in laying their eggs on the very same plants that they (and their parents) experienced as larvae. This provided the scientists with proof of the adaptation process. In their study, the scientists used cabbage as a host plant and added either a large or a small quantity of nitrogen to it, bearing in mind that fertilization with nitrogen is favorable for the development of butterfly larvae. Although the plant containing more nitrogen therefore represented the better choice, females that had developed as caterpillars on plants with less nitrogen showed a tendency to lay their eggs on the unfertilized cabbage.

Accelerated speciation

This kind of breeding behavior has implications for our understanding of evolutionary and ecological processes. The conditioning of the offspring to the parents’ own experiences only takes place if the offspring grow up in a similar environment to the parent generation. In species in which this conditioning occurs, the preference for the corresponding experience is therefore reinforced with each generation. This breeds offspring that are increasingly better adapted to the respective host plant, even if this actually doesn’t provide optimal conditions — and, as a result, new species can emerge more quickly and more easily.

Although the conditioning may have succeeded in reducing the disadvantage caused by the less-favorable environment, it has not eradicated it completely. In compensation, females that accept or even prefer the disadvantageous environmental conditions have access to a greater selection of plants on which to lay their eggs, which leads to a reduction in competition within the species.

Summary:According to a well-known theory in evolutionary biology healthy females should give birth to more males than females. A study shows why this is not always true.

According to popular belief, whether you have a baby girl or boy is purely a matter of chance. And yet, a study published several years ago shows that mothers in stressful jobs, for instance, give birth to more girls than boys. The correlation between such shifts in the offspring sex ratio and the mother’s overall state is something that evolutionary biologists are familiar with from other animal species. One influential hypothesis puts natural selection as an explanation for the imbalances observed.

Strong males with high reproductive success

The Trivers-Willard hypothesis states that it is beneficial for mothers to be able to adjust the sex of their offspring in response to their own state of health. Accordingly, a female in good condition should give birth to more male offspring. This is because successful males have the potential to produce more children in their lifetime than successful females. By producing strong sons, healthy mothers increase the probability of their own genes being widely distributed. Conversely, low-ranking females who are not in such good shape are more likely to produce daughters, because the chances of giving birth to a future dominant male are poor.

“However, it’s not quite as simple as that,” points out biologist Peter Neuhaus sponsored by the Swiss National Science Foundation, based at the University of Calgary in Canada. Taking the example of a model with data from Columbian ground squirrels and Canadian bighorn sheep, Neuhaus — together with colleagues from the UK, the US, France and South Africa — has demonstrated in an article published in Nature magazine that optimal reproduction also depends on a series of other factors.

Dead before reaching sexual maturity

Bighorn ewes, for instance, give birth to only one lamb a year. Most females mate with the dominant ram, which means many of the other males don’t get a chance. Females in a good state often pass on their condition and so can be expected to “to make supermales,” as Neuhaus explains. Nonetheless, the healthy females do not produce more male than female offspring. As the model demonstrates, other parameters, such as the fact that a large number of males die before reaching sexual maturity, play a central role in assessing reproductive potential.

But what have sheep got to do with mothers in jobs with some degree of stress? Nobody doubts that they have more girls, but Neuhaus advises caution: “Evolution is very complex. To understand how it works, you need to take into account as many factors as possible that could influence reproductive potential.”

Males with low quality partners put more effort into parental duties to compensate for the shortcomings of their mate, and pay the price by dying younger

Date:

September 22, 2015

Source:

eLife

Summary:

Non-genetic inheritance plays a huge role in determining the characteristics of offspring. For example, bad parenting creates bad parents-to-be, while well-cared for larvae mature into high quality parents.

When a good insect father pairs with a bad mother, he risks being exploited by her for childcare and could bear the ultimate cost by dying young.

A new study carried out with burying beetles also shows that bad parenting creates bad parents-to-be, while well-cared for larvae mature into high quality parents.

The research will be published in the journal eLife.

“Parents obviously play a huge role in determining the characteristics of their offspring,” says lead researcher Professor Rebecca Kilner from the Department of Zoology at the University of Cambridge.

This is important because non-genetic inheritance could speed up the rate at which animal behaviour evolves and adapts in a rapidly changing world.

Whether examining mothers or fathers, the research team found that individuals that received no care as larvae were less effective at raising a large brood as parents, and died younger. In contrast, high quality care not only produces a larger brood, but individual offspring with a higher mass. This is consistent with previous studies.

“We found that parental care provides a mechanism for non-genetic inheritance. Good quality parents produce offspring that become good parents themselves, while offspring that receive poor parenting then become low quality parents. Our experiments show how parental care allows offspring to inherit characteristics of their parents, but non-genetically,” she says.

However, the team also found that offspring pay a cost for receiving high quality care, because it makes them vulnerable to exploitation if they pair up with a lower quality partner. This may explain why animals often choose a mate who is willing to put in a similar amount of effort as they as a parent. In this way, they are less vulnerable to exploitation.

The burying beetle, Nicrophorus vespilloides, uses the carcass of a small vertebrate such as a mouse as an edible nest for its young. As its name suggests, a breeding pair buries the carcass and preserves it with an antibacterial secretion. The mother lays eggs nearby in the soil, and the larvae crawl to the carcass when they hatch. Although the larvae can feed themselves, they also beg both parents for partly-digested food from the carcass.

In the current study, when males were paired with females that had received no post-hatching care as larvae, they had significantly shorter lives than those whose partners had received more care. The most likely explanation is that males with low quality partners put more effort into parental duties to compensate for the shortcomings of their mate, and paid the price by dying younger.

Story Source:

The above post is reprinted from materials provided by eLife. Note: Materials may be edited for content and length.